MAYDAY in the Everglades

Hello everyone.



The end of my story is this; We landed safely in the middle of the Florida
Everglades and didn't get a single Alligator bite. Here's what happened;



On Friday, April 29th, we took our Cessna 152 from Lantana, Florida to the
center of the State for gas and start our trek south to Key West. The total
journey is a little over 2 hours.



Forty five minutes after filling with gas in Pahokee, we were just below
Alligator Alley (highway 75). Our engine hiccupped. A few minutes later, it
hiccupped again, this time losing a couple of hundred RPM. We were at 6,800
feet, strait and level flight running at 75% power (about 2350 RPM). The
mixture had been leaned back about 30 minutes earlier, and none of the
engine instruments had changed from the time we made our cruise altitude.



As the hiccups got closer together engine power dropped off significantly,
grabbing our total attention. My first move was pulling up on the yoke to
maintain altitude. I trimmed to our plane's best glide of 60 kts When the
sputtering became a constant rough drone, the engine still held some power,
and we could see nothing but marsh. I though about the choice between
ditching in green or brown muck, not sure where the biggest alligators live.
There was absolutely no solid ground as far as the eye could see. Solemnly,
I rolled the 'standby' frequency to 121.5 acknowledging the severity of our
predicament.

Acting on the premise that the engine could quit at any moment and our best
option was behind us on highway I75, I started a very gentle 180 degree
turn.



Oil pressure was in the green. Oil temp was in the green. Mags were on BOTH.
The fuel showed close to full (I had at least 18 gallons useable). My only
immediate change was to push the mixture to full rich, which had no effect.
When I touched the throttle to add power, the RPM dropped. Gently, I
returned the throttle and the power evened out.



The sky was clear, and when I got my pre-flight briefing, the temp was 26
and dew point 16. It was unseasonably cool and very dry for Florida. At
altitude, I knew the air had almost no moisture, but on the way up, we did
have a typical hazy layer. My next move was carb heat, even though there was
absolutely no visible moisture. It did smooth out the roughness slightly,
but did nothing for the power loss.



The engine was dying, and the math was simple. Sink at 500 fpt, 6,800 feet
gives me about 13 minutes and at 60 kts, I'd get about 15 statute miles. I
knew I could make the highway without an engine.



I've personally had experience looking for downed aircraft in the Florida
swamp, and know how difficult it is to spot a small plane. We needed to let
someone know our position and situation. We had the skill to find the
closest airport but every moment was precious. ATC could save valuable
minutes and that might make the difference. With this in mind, I hit the
radio's flip-flop button and announced our tail number on the emergency
frequency.



The Controller was a true professional. He asked me a few questions and
instructed me to "ident" before assigning a squawk code. The radio reception
was not clear, which generated a stream of "say agains". This, of course
added to the general stress of the situation.



Efficiently, he ascertained our position and vectored me to the Dade-Collier
airport, which is in the middle of nowhere. Ironically, so were we! The
strip was 17 miles to our southwest, which is farther than a dead engine
would take me. We had been heading due north to a safe landing point on I75
when ATC advised us to turn our backs on the hwy and return south. In my
heart, we turned away from solid ground to face only swamp again. I decided
to trust fate and the ATC controller as I asked the alligators to gift me
the extra minutes of engine power needed to make the airport.



Trimmed back to slow flight, we managed to barely maintain altitude. We
arrived at the 10,500 foot runway with 3,200 feet of altitude and 120 kts of
air speed. I figure I could have made 4 complete turns around the pattern
and still land hot. I have never been so relieved in my entire life.



On the ground, we taxied to an area near two other planes. Relieved and
curious I did a runup and the engine gave a text book performance.



Our cell phones didn't work so we called the FBO on the radio. We were
invited into the small building nearby where there was a phone. There we
learned that the other two planes had landed the day before with similar
symptoms.



I phoned my mechanic and relayed the story. He gave me some great advice and
a definite suggestion about what caused the problem. We returned to the
plane to follow my mechanics instructions.



Another mechanic, who had come to pick up one of the other downed planes
kindly offered to look at my engine. He pulled the cowl open, checked the
cables on the throttle, carb heat and mixture. He sat in the 152 with me
while I did a regular and then full-power run up. The engine showed great
response to throttle, the mixture choked it and the carb heat performed as
advertised.



This qualified mechanic was planning to fly out in a plane that landed in
the same condition as ours. They offered us a ride if we were not
comfortable flying our 152. We had options. Now, we had to make a decision
to take the ride or hop in our plane and head out.



The logic was: someone at some point would fly our 152 out, and we would
again need to fly this same plane at some point ourselves. If we waited,
what would be different? A qualified mechanic not only said it was safe, but
was flying out a plane in the same condition. We decided the problem had
resolved itself. We would fly.



After a lengthy check, we headed for the runway. I did a steep climb over
the field, continued uphill after completing a long, slow circuit of the
airport, and headed north with a 500 FPM climb. All the while, I knew I
could glide back to the runway if needed.



It was late to start our day in the Keys so we turned towards home. When We
sighted I75, I knew I was home free. If there was trouble we were guaranteed
a level spot to land. We made Lantana at full power with no sign of the
earlier problem.



I must say, I am impressed with the FAA system and the people who dedicate
their careers to the safety of our skies. This system that trains and relies
on the good judgment of the individual pilot also supports the decisions
necessary in crisis. While part of the mandate of the FAA is to enforce the
laws, a pilot's decisions are respected even when they are examined. I find
great comfort in the FAA and the service it provides to general aviation.



If our highways resembled our skies, perhaps the average driver would be
less likely to knowingly break the law.



Here's my question to this group. What caused the engine failure? More than
one thought is welcome, but please explain your answer. I have one of two
possibilities in my head, and invite any questions, advise, opinions, or
wisdom.



Warm regards from one very happy pilot.



Marty

Carb ice. Of course, I wasn't sitting there with you so its just an arm
chair opinion. You say the carb heat worked as advertised but did you
turn it on?

Fuel venting. I'm trying to remember how a 152's fuel is vented. Is it
vented caps or a venting tube? It could have gotten a bit plugged by
dead bugs moving around. If you havent' already, I would remove the
caps and blow air into the tank to see if there is any restrictions.

Great job of handling an uneasy situation with professionalism.

-Robert, CFI

I'll agree to the carb ice... and sometimes.. if heat applied to late.. it
does not work..

one can expect the engine to run rougher after initial application of carb
heat.. while the engine swallows the ice and water... then a marked
improvement... sometimes people get the rougher engine and immediately turn
the carb heat lever back to off and not give it a chance..

BT

"Robert M. Gary" wrote in message
ups.com...
Carb ice. Of course, I wasn't sitting there with you so its just an arm
chair opinion. You say the carb heat worked as advertised but did you
turn it on?

Fuel venting. I'm trying to remember how a 152's fuel is vented. Is it
vented caps or a venting tube? It could have gotten a bit plugged by
dead bugs moving around. If you havent' already, I would remove the
caps and blow air into the tank to see if there is any restrictions.

Great job of handling an uneasy situation with professionalism.

-Robert, CFI

Thanks so far for the responses. To elaborate;

The late model C152 (mine's a 1982), has a fuel vent for the left wing and a
vent cap for the right side. I can blow bubbles up the vent tube, and in
fact a primary consideration during my event was wing vaccuum. My head went
to the wings, but I realized fuel starvation was more likely from a clogged
fuel filter, or pinched line. There's no pump, just gravity.

Regarding carb ice -
Immediately after pushing the mixture to full rich without result, I added
carb heat. It did very little, but I left it in, which is almost against my
religion as it simply fouls plugs in the Florida climate, and little else.
My thoughts on this one are simple; I'm at altitude on a brisk clear day,
with NO VISIBLE MOISTURE. There was some cloud cover above (I estimate
10,000 + altitude). The effect of carb icing is simple - a gradual decrease
in power with engine roughness, which is exactly what I experienced. The
problem was, I had no further power reduction when I added carb heat, which
typically occurs as the ice turns to water and temporarily fouls ignition. I
should have seen an increase in power as the water blew through the carb.
Also, why did adding throttle cause an RPM drop? Is this consistent with
carb iceing?

Also keep in mind that my flight was stable for about 30 minutes when the
hiccup started. I hadn't flown through a cloud and there was no turbulance.

I'll wait for some further input before adding my conclusion and the
subsequent decision to take the plane back into the sky.

Marty

Marty
Forty five minutes after filling with gas in Pahokee, we were just below
Alligator Alley (highway 75). Our engine hiccupped. A few minutes later, it
hiccupped again, this time losing a couple of hundred RPM. We were at 6,800
feet, strait and level flight running at 75% power (about 2350 RPM). The
mixture had been leaned back about 30 minutes earlier, and none of the
engine instruments had changed from the time we made our cruise altitude.

As the hiccups got closer together engine power dropped off significantly,
grabbing our total attention. My first move was pulling up on the yoke to
maintain altitude. I trimmed to our plane's best glide of 60 kts

Good! Exactly correct for step one on the "Power Loss in Flight"
checklist.

When the
sputtering became a constant rough drone, the engine still held some power,
and we could see nothing but marsh. I though about the choice between
ditching in green or brown muck, not sure where the biggest alligators live.
There was absolutely no solid ground as far as the eye could see. Solemnly,
I rolled the 'standby' frequency to 121.5 acknowledging the severity of our
predicament.

Acting on the premise that the engine could quit at any moment and our best
option was behind us on highway I75, I started a very gentle 180 degree
turn.

Oil pressure was in the green. Oil temp was in the green. Mags were on BOTH.
The fuel showed close to full (I had at least 18 gallons useable). My only
immediate change was to push the mixture to full rich, which had no effect.
When I touched the throttle to add power, the RPM dropped. Gently, I
returned the throttle and the power evened out.

The sky was clear, and when I got my pre-flight briefing, the temp was 26
and dew point 16. It was unseasonably cool and very dry for Florida. At
altitude, I knew the air had almost no moisture, but on the way up, we did
have a typical hazy layer. My next move was carb heat,

You got this far before you tried step two!

even though there was absolutely no visible moisture.

The "power loss in Flight" checklist for the 152 says nothing about visible
moisture...just do what it says! You took way too long to try carb heat. From
what I understand, there are two reasons for using carb heat in the 152: 1) the
obvious one and, 2) It bypasses the air filter giving you an alternate air
supply for the engine.

Other than that, you did a good job. I also fly out of Lantana and may fly
that same plane.


See you there,
Vaughn

i can't imagine you would drop in the stuff about 2 other planes
arriving with similar symptoms if the mechanic there to ferry one back
out didn't have a theory that gave both of you enough confidence to
fly.

with those temperatures, izzit possible that you're dealing with ice in
the tanks?

dan

"Marty from Sunny Florida" wrote in message
...
... We were at 6,800 feet, strait (sic) and level flight running
at 75% power (about 2350 RPM) ...

Peculiar cruising altitude, BTW (the glades aren't above
3800 feet, are they?) ...

when I got my pre-flight briefing, the temp was 26 and dew
point 16. It was unseasonably cool and very dry for Florida.
At altitude, I knew the air had almost no moisture,

With temp 26, dew point 16, there's definitely moisture
there. Cool that air down to 16, and you'll start to get
condensation.) At 6800 feet the OAT would have been
cooler and the spread less.

... My next move was carb heat, even though there was
absolutely no visible moisture.

NB: There is absolutely *no* requirement for 'visible
moisture' for carb ice to occur.

It did smooth out the roughness slightly, but did nothing
for the power loss. ...

As others have observed, this is entirely consistent with
carb icing, and (if you didn't (you didn't actually say)) you
should have left the carb heat on.

The unusual cold (for Florida) and the couple of planes
that had the same problem the day before would suggest
this as well. It's lookin' like Florida doesn't get enough
experience with carb icing. (I'm not criticising, just
jealous.))

But good job!, and good story.

"Marty from Sunny Florida" writes:

[...]
The sky was clear, and when I got my pre-flight briefing, the temp was 26
and dew point 16. It was unseasonably cool and very dry for Florida. [...]

If these are in degrees Celsius, then there is ample moisture in the air.

My next move was carb heat, even though there was absolutely no
visible moisture. [...]

You misunderstand the nature of carb icing. Visible moisture (rain?
cloud? thick mist?) is not a prerequisite.


- FChE

Marty from Sunny Florida wrote:

Here's my question to this group. What caused the engine failure?

Carb ice. The only two things that I can think of that can cause those symptoms
in several aircraft at the same time are ice and fuel contamination. Fuel
contamination doesn't go away after you land, therefore it was carb ice. The
reason carb heat didn't melt the ice is that you didn't use it soon enough. By
the time you got the heat on, the engine had been running at low power long
enough to cool off.

George Patterson
There's plenty of room for all of God's creatures. Right next to the
mashed potatoes.

Carb ice. As the others have said if it's applied too late carb heat may
not have any effect once the ice has accumulated in the venturi. Visible
moisture is not necessary for carb ice, you only need adequate humidity and
according to Lycoming temps between 20 and 90 degrees F. Continental
engines can form carb ice at even higher temps due to the position of the
carburetor and remember that warmer air can hold more moisture than cold air
so when carb ice develops at high temperatures it can be more severe. A
full rich mixture can create carb ice even easier because now the carburetor
is vaporizing more fuel creating a greater temperature drop. Adding
throttle (fuel) can also cause an increase in carb ice due to the additional
drop in temperature caused by the additional vaporizing fuel. After you
landed and taxied around at relatively low RPMS (low amount of fuel
vaporizing, warmer carb temps) the problem disappeared. Beware of it
re-occurring on take off when you pour huge amounts of fuel through that
carburetor again at full rich mixture.

The non-textbook experience you presumably had with carb ice could be
attributed to the engine ingesting chunks of ice departing first the
throttle plate, then later off the venturi itself.

The fact that several other airplanes in the area had the same problems also
leads me to lean towards carb ice.

This is the second post in as many months that has indicated that carb ice
requires visible moisture. Structural ice requires visible moisture. Carb
ice can form in visible moisture but it is not at all necessary. Either
there are a lot of instructors mis-informing students on this matter or the
FAA needs to get out a new AC on carb ice. Maybe both.

Marty you did a great job holding your composure, thinking things through,
and making good decisions. I'm glad you made it to the airport.

Jim